Method:Heat the oil in a saucepan, add the onion, mushrooms, and garlic, and cook for 10 minutes or until soft. Sprinkle in the flour and cook, stirring, for 1 minute.

Add the tomatoes, basil, and sugar, and season with salt and pepper. Cover and simmer for 20 minutes.

Season the spinach with salt and pepper. Taking 1 teaspoonful at a time, shape it loosely into 24 balls.

Spoon one-third of the mushroom mixture into a large ovenproof dish, and place eight of the spinach balls on top. Cover with one-third of the white sauce and one-third of the cheese. Arrange half of the lasagna on top. Repeat the layers, finishing with cheese.

Bake in a preheated oven at 190℃ (170℃ fan, Gas 5) for 35 minutes or until the pasta is tender. Serve hot, accompanied by a mixed leaf salad.